There is a conventional front-and-rear wheel drive vehicle in which a driving force of an engine is transmitted to front wheels as main drive wheels on a constant basis and is transmitted to rear wheels as auxiliary drive wheels at the time of need depending on a running condition of a vehicle (see, e.g., PTL 1).
The front-and-rear wheel drive vehicle disclosed in PTL 1 is provided with a driving force transmission device for transmitting a driving force output from the engine to the auxiliary drive wheels and has a function of controlling torque to be transmitted to the auxiliary drive wheels based on a throttle opening degree or a difference in rotation between front and rear wheels.